1. Field of the Invention
The present invention relates to a method of gasifying organic materials (carbonaceous compounds) such as coal and fossil fuel and their mixtures including gasifying wastes into syngas, and an apparatus thereof.
2. Description of the Related Art
The reforming/gasification reaction is an endothermic reduction reaction and reaction heat must be supplied continuously for sustained operation. Furthermore, this reduction reaction is very slow at temperatures below 1200° C. See Kim, Hyun Yong International Journal of Hydrogen Energy, Vol. 28/11, pp. 1179˜1186.
In the conventional method of gasification, oxygen gas is pumped into the gasification reactor to burn portions of carbonaceous feed material, and the heat generated from the combustion is used to maintain the reactor furnace at the elevated temperature. Further, an externally heated steam is supplied to promote gasification and to increase the concentration of hydrogen in the produced syngas. At any temperature below 1200° C., the reaction is extremely slow and metal catalysts are often used to promote the gasification.
U.S. Pat. No. 6,120,567 issued on Sep. 19, 2000, U.S. Pat. No. 6,084,147 issued on Jul. 4, 2000 and U.S. Pat. No. 6,001,144 issued on Dec. 14, 1999 describe the conventional steam reformation method of injecting O2 gas and carbonaceous material into various two stage reactor to accomplish reforming reaction of organic material.
Also, U.S. Pat. No. 5,980,858 issued on Nov. 9, 1999 and U.S. Pat. No. 6,063,355 issued on May 16, 2000 describe a two stage steam reforming reactor to produce H2 gas and leading to the production of NH3 gas. U.S. Pat. No. 3,823,227 issued on Jul. 9, 1974 and U.S. Pat. No. 3,759,677 issued on Sep. 18, 1973 describe gasification by steam reformation of solid waste materials including solid municipal waste. The gasification reaction is carried out in the presence of an alkali metal carbonate catalyst at a temperature between 427 and 871° C.
In all of the above cases, where the reactor temperature does not reach 1200° C., very little of reformation/reduction reaction takes place, and production of syngas is minimal at best.
The oxidation reaction which takes place in gasification is indicated as follows:C+O2→CO2   (1)2(—CH2—)+3O2→2H2O+2CO2   (2)
Reaction 1 indicates the combustion reaction that usually occurs in coal whose main component is carbon, and Reaction 2 is the main combustion reaction occurring with carbonaceous material such as fossil fuel.
The requirement of oxygen, which varies with the aspect of coal (C) or fossil fuel (—CH2—) supplied into the reactor, amounts to 0.5˜1.0 weight of the coal or fossil fuel. The oxygen supplied into the reactor is consumed according to Reactions 1 and 2 to increase the reactor temperature and produce combustion products, H2O and CO2.
The combustion products reduce all carbon atoms of coal as shown in Reactions 3 and 4. The gasification reaction requires longer reaction time as compared with combustion reaction and higher temperature to continue the reaction. The gasification reactions of organic material such as fossil fuel (—CH2—) are shown as Reactions 5 and 6.C+H2O→CO+H2   (3)C+CO2→2CO   (4)(—CH2—)+H2O→CO+2H2   (5)(—CH2—)+CO2→2CO+H2   (6)
While the Reactions 1 and 2 are oxidation reactions, the Reactions 3 to 6 are reduction reactions. The gas produced from the reactions 3 to 6 is syngas whose main components are CO and H2. Under the reaction condition of 1200° C. and higher, all carbon atoms and hydrogen atoms in the reactor are effectively reduced to CO and H2 gases. And no other carbon atom of any other oxidation state can remain in the reactor. Syngas is the dominant product.
In conventional gasification methods, gasification or reforming reactions (Reactions 3 to 6) utilize the exothermic heat of oxidation reactions (Reactions 1 and 2) which is induced by oxygen supplied with coal or carbonaceous material, in order to maintain the temperature of the gasification reactor. Further, an additional supply of steam is often required to increase the concentration of syngas. The steam is acquired by means of heat exchange with the output syngas.
As described in the above, in conventional gasification methods, oxidation reactions (Reactions 1 and 2), and reduction reactions (Reactions 3 to 6) occur concurrently in the same space, and therefore, the production of syngas is minimal and secondary pollution from the oxidation of feed material usually occurs.
KR. Pat. No. 0391121, Jun. 30, 2003 and U.S. Pat. No. 6,790,383 B2. issued on Sep. 14, 2004, titled “METHOD OF GASIFYING CARBONACEOUS MATERIALS” describes a gasification method and apparatus where carbonaceous compounds such as coals, shredded waste tire or waste oil are gasified into gaseous fuel, CO and H2. According to this apparatus, the reformer body (reduction reaction chamber) and the syngas burner (oxidation reaction chamber) are stacked vertically as shown in FIG. 1. With this configuration O2 gas containment within the syngas burner is not completely assured. As the throughput of the reformer is increased, more of O2 gas in the syngas burner escapes into the reduction reaction chamber, without being completely consumed within the syngas burner. Further the input port for the solid feed stock is placed at the upper portion of the reduction reaction chamber body. However, this is not the optimal placement of the solid feed stock since this is not the coolest place in the reformer body. The coolest place is at the bottom of the reformer body.